1. Field of the Invention
This invention relates to a shock absorber for use with the front suspension fork of a mountain bike or the like, including a housing having a chamber containing independently operable compression, rebound and lockout piston means, said lockout piston means being arranged in the housing on the opposite side of said compression piston means from said rebound piston means, and a lock-out valve manually operable by the user between a closed lockout condition in which the lockout piston means is activated for operation upon the occurrence of a severe compression overload condition, and an open condition in which the lockout piston means is de-activated. The operation of the lockout piston means is independent of the operation of the compression piston means.
2. Brief Description of the Prior Art
Various types of shock absorbers for use in mountain bicycles have been proposed in the patented prior art, as evidenced, for example, by the prior patents to Turner U.S. Pat. Nos. 4,971,344, 5,186,481, and 5,580,075, Yamaoka U.S. Pat. No. 5,246,092, and Dohrman et al U.S. Pat. No. 5,195,766, among others.
It is well known in the art to provide manually-operable adjustment means for controlling or customizing the operation of the shock absorbers in accordance with the size and/or weight of the rider, or with the nature of the expected riding conditions. For example, as illustrated in FIGS. 1 and 1A of the accompanying drawings, in the MANITOU TPC Twin Piston Chamber shock absorber produced by Answer Products, Inc., of Valencia, Calif., the assignee of the instant application, a shock absorber is provided having a housing defined by a pair of telescopically-arranged cylinders and containing compression and rebound piston means that define therebetween a main central chamber containing a damping fluid, and compression and rebound chambers on opposite sides of said main chamber, each of said compression and rebound piston means being provided with manually-operable adjustment needle means for controlling the flow of damping fluid from the main center chamber to and from the compression and rebound chambers during the compression and rebound strokes of the shock absorber. This prior shock absorber is the subject of the Gonzales et al U.S. patent application Ser. No. 09/081,157 filed May 18, 1998, which is a continuation application of application Ser. No. 08/725,409 filed Oct. 3, 1996.
Similarly, the shock absorber of the Turner U.S. Pat. No. 5,186,481 illustrated in FIG. 2 of the drawings includes an adjustment knob for varying the preload of a biasing spring to compensate for a full variety of rider weights and abilities. In the Yamaoka U.S. Pat. No. 5,246,092, as shown in FIG. 3 of the drawings, a rotary control valve is provided for adjusting the opening areas of orifices of an hydraulic shock absorber of a vehicle, thereby to change the magnitude of the various damping compression and rebound forces as desired. A recent front fork suspension system for mountain bikes including manually-operable lockout means is the RUBY SL fork manufactured by RockShox, Inc. of San Jose, Calif.
During certain riding situations, like steep climbing or racing on level ground, it has been found that restricting movement of the suspension fork can improve the pedaling performance of the rider. The present invention was developed to provide an improved shock absorber of the twin piston chamber type for mountain bikes, wherein the operation of the shock absorber is improved by providing a selectively-operable lockout piston that is connected in-line with the compression piston, manually-operable means being provided for selectively operating the shock absorber between a closed lockout condition in which the lockout piston is activated and the compression piston is substantially de-activated, and an open condition in which the lockout piston is de-activated and the compression piston operates in its usual manner.